A signature-based Approach for efficient relationship search on XML data collections

We study the problem of finding relevant relationships among user defined nodes of XML documents. We define a language that determines the nodes as results of XPath expressions. The expressions are structured in a conjunctive normal form and the relationships among nodes qualifying in different conjuncts are determined as tree twigs of the searched XML documents. The query execution is supported by an auxiliary index structure called the tree signature. We have implemented a prototype system that supports this kind of searching and we have conducted numerous experiments on XML data collections. We have found the query execution very efficient, thus suitable for on-line processing. We also demonstrate the superiority of our system with respect to a previous, rather restricted, approach of finding the lowest common ancestor of pairs of XML nodes.